The invention relates to digital telephony. More particularly, the invention relates to mobile switching centers, IP telephony, hosted PBX, and enterprise PHS networks.
In one known solution of remote call forwarding (RCF), a customer calls a telephone number that, unknown to the caller, has been forwarded to a new location. The customer's originating local exchange parks the call while it initiates a signaling message to the apparent terminating local exchange. When the signaling message arrives at the original terminating local exchange via the CCS7 network, the switch polls the customer line to determine its status (e.g., whether the customer line is available, busy, or forwarded). If the line has been forwarded, a look-up table is consulted to determine the new location of the number, and a new signaling path is established. To establish a new signaling path, another signaling message is sent to the new apparent terminating local exchange, and the process is repeated until the correct terminating customer line has been identified. If that line is available, the switch returns a message to the originating exchange to indicate that all is ready for call completion. The call is then released by the originating switch and is routed along the same path as that previously traversed on the signaling network.
Problems with this on-switch solution of remote call forwarding include the limitation of the service to a single system. Moreover, the call path (or at least the signaling path) must be completed before a ported number is recognized. This results in inefficient cal routing, which for large volumes of ported numbers can become unacceptable.
In another solution, known as off-switch, switches involved earlier in the call set-up phase are allowed to access information about ported numbers. In this solution, a customer calls a telephone number that may or may not have been ported to a new location. The customer's originating local exchange (known in the IN architecture as the Service Switching Point, or SSP) parks the call while it initiates a CCS7 signaling message to the IN database at the Service Control Point, SCP. When the signaling message arrives at the SCP, the database is consulted to determine the network address or routing number associated with the dialed telephone number. The SCP returns the routing information to the SSP. The SSP then transmits a signaling message to the terminating exchange to determine whether the called party is available. The call is released by the SSP, and the call path is established over the optimal route to the terminating local exchange.
With such off-switch solutions, there is no equivalent to the terminating database solution for non-geographic services. Moreover, they do not provide a method for linking the services of a user who is subscribed to multiple service providers onto one device, application, or location.
Prior solutions also suffer the disadvantage of an assumption of quality circuit connections that do not exist in ad hoc Internet connections. Instead, quality of service is assumed to the endpoint.
Various IP telephony solutions are known in the art. For example, White et al., U.S. Pat. No. 6,069,809, teaches telephone type services over the Internet. White et al., U.S. Pat. No. 6,021,126, teaches using the Internet for telecommunications number portability. White and Ferris, U.S. Pat. No. 6,014,379 teaches telecommunications custom calling services over the Internet. Kalmanek, et al., U.S. Pat. No. 6,324,279, teaches signaling to link two dissimilar systems for IP telephony. All of these disclosures are incorporated herein by reference. These solutions, however, do not provide a method for linking services of a user subscribed to multiple service providers onto one device.